The present invention relates to a self-damping bar pusher rod for bar feeders and is used in particular in bar feeders for automatic lathes.
It is known that in automatic lathes the bar to be machined is made to advance by means of a bar pusher which consists of a rod provided, at its front end, with a collet for retaining the rear end of the bar to be machined. The machining of the bar entails its advancement through the tubular spindle of the lathe up to an abutment which determines the length of the portion to be machined. After the bar has stopped against the abutment, it is gripped by the collet of the spindle in order to be turned or to undergo other machining operations.
The problem that currently occurs in automatic lathes is that the time available to make the bar advance is increasingly limited, since it is considered to be unproductive. In order to reduce the advancement time, in the absence of suitable devices in the lathe, the bar advancement speed is increased. However, this increase causes the bar to rebound off the abutment of the lathe and, if the opening time of the collet of the lathe is short, when the collet closes again the bar often is not arranged against the reference abutment and accordingly the machined part is shorter and must be rejected.
The solutions used so far to eliminate this drawback consist in providing rebound-preventing devices which act on the motorization system of the bar pusher, but these have proved to be insufficient in addition to being uneconomical in relation to the result achieved.